The invention relates to a probe device for determining the concentration of highly volatile components in liquids and/or gases, with a probe body comprising a probe core and a probe finger being permeable for the highly volatile components, in the area of the probe core or of the probe finger a sensor for the highly volatile components being provided, and comprising a protective tube enclosing the probe finger and having passage openings. Such probe devices are particularly used in the fields of process supervision and/or process control of chemical and bio-technological processes. The concentration of one or several highly volatile components in a reaction space is measured, and the process is controlled and/or regulated according to the determined concentrations. Highly volatile components are substances the boiling points of which are typically lower than that of water. Examples for such substances are C1 to C8 hydrocarbons, C1 to C6 alkyl monoalcohols, C1 to C6 alkyl aldehydes, C1 to C6 alkyl ketones. C1 to C6 alkyl carboxyl acids, benzole, alkyl-substituted benzole, phenols etc. Oxidizable highly volatile compositions are in particular measurable. The sensor is sealed against the environment, and highly volatile components have access to the sensor over the permeable probe finger only. Sensors are for instance commercially available semi-conductor detectors and the like. The permeability of the probe finger is established by that over the probe finger having cutouts a suitable permeable material covering said cutouts is provided. Such permeable material is typically configured as a permeation membrane, and with regard to the material selection, an adjustment to the highly volatile component to be measured is easily made by the average man skilled in the art. The protective tube serves for the protection of such a permeation membrane from mechanical damage.
A probe of the construction mentioned above is for instance known in the art from document EP 0 174 417 B1. The insofar prior art probe has proven excellent. It has been shown, however, that this probe can be improved in terms of handling. In the prior art probe, fixing in a flange of a reaction vessel takes usually place by means of for instance a cap screw, with the probe finger extending into a reaction space. It is disadvantageous herein that for cleaning or maintenance operations at the probe and/or the probe finger, the whole probe has to be removed by hand, which is very time consuming. Further it is disadvantageous that in the course of the disassembly (and the reassembly) of the probe the reaction vessel remains open for a certain period of time. This is disturbing particularly for bio-technical processes, since bio-technical processes are subject to special requirements with regard to sterility (safety against contamination of the reaction space by micro-organisms disturbing the process and/or internal environment.
Therefore, the invention is based on the technical problem to provide a probe for determining the concentration of highly volatile components, said probe being easily insertable into a reaction vessel and also easily removable therefrom and whereby in bio-technical processes a contamination of the reaction space for instance in the course of a probe finger cleaning operation is virtually excluded.
For solving this technical problem, the invention teaches that the protective tube is configured as a piston of a sluice device having a measuring position and a servicing position of the piston, and that passage openings of the piston are disposed such that the piston has in addition the function of a slider valve sleeve, with the probe finger being connected over the passage openings in the measuring position to a measuring space and in the servicing position to a servicing space separated from the measuring space. As a piston is designated a structure that can slide forwards and backwards in cylindrical guiding surfaces, with external sealing surfaces. The measuring space is normally formed by the reaction space of a process. Sideways to the measuring space is connected a servicing space to be sealed in a gas-tight manner. By an embodiment of the invention, the protective tube obtains two functions. On one hand, a function as a piston is established, and on the other hand, as a slider valve sleeve. The protective tube is thus simultaneously a slider valve sleeve and a drive element therefor. As a result it is achieved that by means of the protective tube, the probe finger can be brought in connection alternatively with the measuring space and the servicing space. It is understood that the servicing space can in turn be operated such that a contamination cannot take place. In practical applications, service of the probe is made as follows. During measurement, the protective tube connects the measuring space through the passage openings to the probe finger, and simultaneously separates the measuring space from the servicing space in a gas-tight manner. By forward drive of the protective tube configured as a piston, a displacement of the protective tube will take place, the probe finger being separated from the measuring space and connected to the servicing space. In the servicing position, the measuring space and the servicing space are hermetically sealed against each other. The servicing space typically permits access and discharge of (sterile) cleaning agents and the like. After service, the process is reversed, as described above, and the probe now after service is again connected to the measuring space.
It is achieved, by the invention, that the measuring space will in the course of maintenance of the probe or reassembly of the probe not at any time come into contact with a contaminated environment. Further, maintenance of the probe finger can be made without a time-consuming removal of the probe.
In a preferred embodiment of the invention, the sluice device is pneumatically operable, a cylindrical space being provided where the piston including a piston ring is slidable forwards and backwards between the measuring position and the servicing position by alternating pressure application on different sides of the piston ring. Such pneumatically operable sluice devices are per se known in the art from practical applications in conjunction with pH probes. Basically, however, other drive systems, such as electro-magnetic and/or electro-motoric, are also possible, then in the area of the probe and/or of the piston suitable mechanical drive elements having to be provided, such as spindle gears.
It is recommended that the servicing space comprises at least one part for rinsing fluids. Rinsing fluids may for instance be liquids or gases. Sterilized water may be used, if necessary with usual additions for cleaning. Moreover, corresponding to the process to take place in the measuring space, various rinsing fluids are possible. Care should only be taken that a rinsing fluid will not affect for chemical or bio-chemical reasons the process taking place in the measuring space, since during the displacement of the protective tube between the measuring position and the servicing position a connection between measuring space and servicing space will exist for a short time. Typically, the servicing space will comprise two ports for handling the rinsing fluids, a feeding port and a discharging port.
An advantageous embodiment with regard to the constructional configuration is characterized by that the piston carries the piston ring at the end directed away from the measuring space and/or that the probe core and the piston are connected by a screw connection in the area of the piston ring. It is recommended that the probe core extends immediately adjacent to the piston ring by at least one piston stroke length L and carries outside at least on one piston stroke length L a probe sealing face. The piston may carry at its end directed towards the measuring space a piston bottom sealing in the servicing position the measuring space in a gas-tight manner against the servicing space. Further, the piston may carry in the area directed towards the measuring space a piston sealing face, by means of which the servicing space is sealed in the servicing as well as measuring positions in a gas-tight manner against the cylindrical space and by means of which the measuring space is sealed in the measuring position in a gas-tight manner against the servicing space. As a result, by combination of the constructional features described above, an embodiment is provided, wherein the piston with assigned sealing elements of the servicing space will seal the latter against the environment. The cylindrical space in turn is sealed at its end directed towards the measuring space against the piston, and at its end directed away from the measuring space against the probe core.
The passage openings in the piston can basically be executed in an arbitrary manner. With regard to a long life of the sealing elements, it is recommended to adapt the passage openings as slots extending in the longitudinal direction of the piston between the piston bottom and the piston sealing face. The pneumatic operation can be performed with any usual pneumatic fluids, an operation by pressurized air (2 to 10 bars, preferably 3 to 5 bars) being preferred.